1. Field of the Invention
The present invention relates generally to flow restrictors, and more particularly to a flow restrictor including a flexible umbrella-shaped one-way check valve and an orifice for controlling the fluid flow therein and within a spark advance and exhaust systems of an internal combustion engine.
2. Description of the Prior Art
Conventionally, a flow restrictor comprising a housing, a partition wall dividing the interior space of the housing into two chambers, a flexible umbrella-shaped one-way check valve, consisting of an umbrella portion which closes or opens a number of circumferentially spaced apertures provided within the partition wall so as to interrupt or establish fluidic communication between the two chambers and a stem portion which is securely received in a valve receiving bore provided within the partition wall at the central portion thereof so as to secure the valve to the partition, an orifice provided within the partition wall for establishing a restricted fluidic communication between the two chambers, and filters arranged on both sides of the orifice, is well known.
This type of flow restrictor, however, has several operational disadvantages, such as, for example, the fact that the orifice is easily plugged or clogged by dust which passes over the outer periphery of the filter, because the orifice is near the outer periphery of the filter.
Furthermore, the flow restrictor is quite large in size, because the umbrella-shaped one-way check valve and the orifice are arranged on the partition wall in a parallel fashion.
Still further, the manner of securing the check valve to the partition wall is difficult.